Pressure sensing mat

Abstract

A pressure sensing sheet includes at least first, second, and third layers wherein the first and third layers each have conductive paths defined therein that are separated by nonconductive spacers. The orientation of the conductive paths of the first layer are transverse to the orientation of the conductive paths of the third layer. The second layer is made of material that has an electrical characteristic that changes with applied pressure, such as, but not limited to, piezoresistive or piezoelectric material. The first and/or third layers are made from multi-material sheets wherein a first type of material will repel conductive particles when subjected to an autocatalytic coating process, while the second type of material will bond with the conductive particles during the autocatalytic coating process. The use of different materials in the first and/or third layers facilitates the manufacturing of the conductive paths and nonconductive spacers.

What is claimed is: 
     
       1. A pressure sensing mat comprising:
 a first layer of fabric having rows of electrically conductive strips separated by nonconductive spacers, said first layer of fabric being made of a first type of material and a second type of material, said first type of material being different from said second type of material, said first type of material and said second type of material being secured together in an end-to-end fashion wherein said first type of material is positioned at said nonconductive spacers and said second type of material is positioned at said conductive strips, wherein said first type of material repels a solution of conductive particles such that when said first type of material is bathed in the solution of conductive particles, said conductive particles do not adhere to said first type of material; 
 a second layer of fabric that includes pressure sensing material; and 
 a third layer of fabric having columns of electrically conductive strips separated by nonconductive spacers, wherein said second layer of fabric is positioned between said first and third layers of fabric. 
 
     
     
       2. The mat of  claim 1  wherein said first type of material and said second type of material of said first layer are woven together. 
     
     
       3. The mat of  claim 1  wherein said first type of material and said second type of material of said first layer are knitted together. 
     
     
       4. The mat of  claim 1  wherein said second type of material is made from a material to which conductive particles in the solution will adhere when said second type of material is bathed in the solution of conductive particles. 
     
     
       5. The mat of  claim 4  wherein said third layer of fabric is made from said first type of material and said second type of material. 
     
     
       6. The mat of  claim 5  where said first type of material of said third layer repels the solution of conductive particles such that when said first type of material of said third layer is bathed in the solution of conductive particles, the conductive particles do not adhere to said first type of material of said third layer; and wherein said second type of material of said third layer is made from a material to which the solution of conductive particles will adhere when said second type of material of said third layer is bathed in the solution of conductive particles. 
     
     
       7. The mat of  claim 1  wherein the pressure sensing material of the second layer is piezoresistive material. 
     
     
       8. The mat of  claim 1  further including an elastically stretchable top cover and an elastically stretchable bottom cover, said top cover and said bottom cover being sealed together at their periphery, and said first, second, and third layers of fabric being enveloped by said top and bottom covers. 
     
     
       9. The mat of  claim 8  wherein said top and bottom cover are elastically stretchable in mutually orthogonal directions by at least ten percent of their length in each of said mutually orthogonal directions. 
     
     
       10. The mat of  claim 1  further including an electronic control module, said electronic control module including circuitry for determining an amount of pressure exerted at a plurality of locations on said mat based upon pressure-induced changes in electrical resistance in said second layer of fabric. 
     
     
       11. The mat of  claim 10  wherein said electronic control module is configured to act as a wirelessly accessible web server such that an electronic device having web browser software can wirelessly access pressure data indicative of the amount of pressure exerted at the plurality of locations on said mat and display the pressure data on the electronic device. 
     
     
       12. The mat of  claim 11  wherein said electronic control module is configured with an IP address that uniquely identifies said electronic control module on a healthcare network. 
     
     
       13. The mat of  claim 10  further including a universal serial bus (USB) cable extending from said electronic control module out of an aperture defined between said top and bottom cover, said USB cable including a connector for connecting to an external electronic structure. 
     
     
       14. The mat of  claim 1  wherein said first type of material is polyester and said second type of material includes nylon. 
     
     
       15. A pressure sensing mat comprising:
 a first layer of fabric having rows of electrically conductive strips separated by nonconductive spacers, said first layer of fabric being made of a first type of material and a second type of material, said first type of material being different from said second type of material, said first type of material and said second type of material being secured together in an end-to-end fashion wherein said first type of material is positioned at said nonconductive spacers and said second type of material is positioned at said conductive strips; 
 a second layer of fabric that includes pressure sensing material; and 
 a third layer of fabric having columns of electrically conductive strips separated by nonconductive spacers, wherein said second layer of fabric is positioned between said first and third layers of fabric; and 
 wherein said first, second, and third layers of fabric are each elastically stretchable in mutually orthogonal directions by at least one percent of their length in said mutually orthogonal directions. 
 
     
     
       16. The mat of  claim 15  wherein said first, second, and third layers of fabric are elastically stretchable in mutually orthogonal directions by at least ten percent of their length in said mutually orthogonal directions. 
     
     
       17. The mat of  claim 15  wherein said first type of material is polyester and said second type of material includes nylon. 
     
     
       18. The mat of  claim 15  further including an electronic control module, said electronic control module including circuitry for determining an amount of pressure exerted at a plurality of locations on said mat based upon pressure-induced changes in electrical resistance in said second layer of fabric. 
     
     
       19. A method of making a pressure sensing mat comprising:
 providing a first layer of fabric having rows of a first type of material secured together with rows of a second type of material; 
 providing a second layer of fabric having an electrical characteristic that changes in response to normal forces applied thereto; 
 providing a third layer of fabric having columns of the first type of material secured together with columns of the second type of material; 
 bathing said first and third layers of fabric in a liquid solution that includes electrically conductive particles, said electrically conductive particles adhering to said second type of material but not said first type of material; 
 positioning said second layer of fabric between, and in contact with, said first and third layers of fabric; and 
 electrically coupling said rows and columns of said second type of material to a controller. 
 
     
     
       20. The method of  claim 19  wherein the electrical characteristic of the second layer of fabric that changes in response to normal forces is electrical resistance. 
     
     
       21. The method of  claim 20  wherein said first material is polyester, said second material includes nylon, and said electrically conductive particles include silver particles. 
     
     
       22. The method of  claim 21  wherein said bathing is an autocatalytic process. 
     
     
       23. The method of  20  wherein said first and second types of material are secured together by knitting. 
     
     
       24. The method of  claim 20  wherein said first and second types of material are secured together by weaving.